It is true that no promotional budget could come close to buying the kind of publicity that Cole's departure from the US X Factor has generated.

But the very messy, in-again-out-again story of the Geordie lass and the evil network bosses may be exactly what it looks like; a very public farce, an illustration of what happens when you go swimming in shark-infested waters. And for Cowell, it could be the clearest confirmation yet that his reign as the transatlantic overlord of prime-time, talent show TV could be coming to an end.

Cut through the blizzard of spin that invariably swirls around anything to do with the 51-year-old TV titan and we may be looking at a circus ringmaster who is beginning to lose control of the lions.

The signs have been there in recent months, with his other marquee show, Britain's Got Talent, hitting a serious ratings wobble shortly after its launch in April.

The opening night of this year's BGT drew an audience of 11.6 million viewers for ITV. But the following week saw ratings drop to 8.99 million viewers, the lowest numbers for the audition stage of the programme since it launched in 2007.

The huge drop in figures was enough to prompt a rumoured crisis meeting, with sources close to Cowell briefing showbiz reporters on his plans to replace new guest-judge David Hasselhoff.

In the end, the surprisingly strong showing of comic Michael McIntyre, another new judge, helped to shore up ratings and prevent the kind of very public dumping that left Cheryl Cole out in the cold.

However, there were more serious concerns for Cowell in the run-up to last weekend's BGT final when he had to publicly and personally deny allegations that he had "fixed" the outcome in favour of 12-year-old Ronan Parke (who in the end lost out to Jai McDowell).

Responding to widely reported allegations made by an anonymous internet blogger who claimed to be a former Sony BMG executive, Cowell had to take a moment on the show to refute what he called "a deliberate smear campaign".

Cowell then went on to tell the millions of BGT fans that he had not, as was alleged, met with Ronan Parke two years ago and signed him to a record deal with his label Sony BMG.

"This is a deliberate smear campaign and it is my job as someone who works on this show to make sure that whoever the liar is, is exposed," he said, sounding more like crisis-hit FIFA boss Sepp Blatter than a judge on a talent contest.

Cowell looked rattled, as you would expect from somebody whose empire is built on ensuring that the greater public buy into the idea that they make or break the stars and there is no wizard behind the curtains involved.

His shows have always won massive newspaper and magazine coverage through the leaking of real or imagined spats, break-ups and backstage bitching involving judges and contestants.

Through the run of any season of X Factor or Britain's Got Talent, fans are treated to a bewildering succession of secret alliances, hatchet jobs and tales of thwarted ambition of a kind last seen when the Borgias were scheming for the papal throne.

But these endless Louis-hates-Sharon-who-can't-be-in-the-same-room-as-Dannii stories always had the air of being nicely controlled and parcelled up for the hungry media and public.

When Cowell is publicly forced to dump Cheryl Cole (as the most plausible explanation has it) or has to take time out from the final of BGT to publicly deny allegations of a fix, it's clear we have gone beyond spin and the cracks are showing.

The Cheryl Cole firing may be the clearest example yet of how Simon Cowell has spread himself too thin and found himself at the mercy of notoriously hard-nosed American network TV executives. Cowell's phenomenal success in the UK, where his shows are credited with keeping troubled network ITV alive as a major player, has ensured his word, deed and command is gospel.

The word from the US is that Cole performed very poorly on the initial filming of the Fox version of the hit UK show.

Cowell, who had staked a lot on making Cole a success in the US, was understood to have argued that she would improve dramatically and even made a last-ditch effort last weekend to persuade her to come back and give it another go.

However, Fox executives are said to have made up their minds and Nicole Scherzinger, the Pussycat Dolls singer who had been a guest on the UK X Factor and was judged to be a much better fit for US audiences, was confirmed as her replacement.

The good news for Cole is that she is still expected to get her full judge's fee, thought to be $1.2m.

But the real victim here (and try to hold back those tears) could be Simon Cowell, who is widely judged to be weakened by the fiasco.

Even worse for Cowell are the reports this week that the BBC and ITV are locked in a bidding war for a new Saturday-night talent show which is being sold as a "kinder, less gimmicky and image-obsessed" version of X Factor.

Billed as the "world's hottest new TV music property", The Voice was devised by Dutch TV tycoon John De Mol (of Big Brother fame) and offers a new twist on a well-worn concept.

The new format has "blind" auditions in which contestants are rated on their singing alone. And the judges are encouraged to hand out more "constructive" criticism rather than the one-line put-downs that made Cowell a star. There is even speculation that both the BBC and ITV want Cheryl Cole to be the chief judge on their version of The Voice.

ITV director of television Peter Fincham -- who is also bidding for The Voice -- is said to see the new format as a replacement for the next series of X Factor, which could perform badly without Simon Cowell as a judge.

Whichever network lands the new show, it's telling that it is being sold as the "antidote" to Simon Cowell's patented brand of talent-show television.

When TV executives are pitching shows on the basis they are the complete opposite to those made by the once all powerful Mr Cowell, it's a sign that the game may almost be up.